1. Field of the Invention
The present invention relates to a laminated (stacked) body of a motor, and particularly, to a laminated body of a motor and its manufacturing method capable of reducing cogging torque in operation of the motor, making no thermal deformation and improving productivity.
2. Description of the Background Art
A conventional motor laminated body of this type is manufactured by stacking a plurality of ring-shaped board members blanked directly from a steel board, as disclosed in JP 57-100823, for instance. However, yield of materials is low. For this reason, JP 57-75551 discloses a method for improving the yield in such a manner that a belt-shaped board member with a large number of teeth is spirally wound and undergoes plastic deformation, and several layers are fastened by welding the respective layers.
In FIGS. 1 and 2, another laminated body, which has a similar structure to the above-mentioned structure, of a motor according to the conventional art, is depicted. FIG. 1 is a perspective view for explaining a laminated state of a laminated (stacked) body of a conventional motor, and FIG. 2 is a plan view showing a laminated body whose lamination is completed, of a motor.
As shown, the laminated body 10 of the motor includes a yoke part 20 having a ring shape; and a plurality of teeth parts 30 protruding from an outer side of the yoke part 20 along a radial direction and disposed in an isolated manner at predetermined intervals so that a winding coil (not shown) can be wound therearound. A stopping protrusion 35 is formed at an end of each teeth part 30 by widening a width of the teeth part so that the wound winding coil is not detached from its mounted position. The stopping protrusion 35 is extendingly formed in a perpendicularly direction to the teeth part 30. As for such a laminated body 10, the belt-shaped yoke part 20 and the teeth part 30 are integrally formed and spirally laminated, and then a plurality of welded portions 40 are formed on an inner circumferential surface of the yoke part 20 so that layers are not separated but fixed. In case of an outer teeth type laminated body 10 depicted in FIGS. 1 and 2, a ring-shaped permanent magnet or the like (not shown) is disposed at an outer circumferential surface of the laminated body 10 at almost regular intervals between itself and the stopping protrusion 35 so as to make a relative rotary motion
In the motor having such a structure, a rotor is rotated in one direction by interaction between flux (generated by property switching or applying a current to the winding coil) and the permanent magnet or the like.
The laminated body of the conventional motor as described above has the following problems.
First, in coupling of the laminated body 10 by means of welding, a defective measurement may occur due to deformation by heat generated in welding, equipment for welding and cooling is required, and many production hours are consumed on welding and cooling. In addition, the welding processing causes a change of material in quality due to heat, whereby generation of flux in operation of the motor may be interrupted.
In addition, in a laminating process, the yoke part 20 is properly pressed to undergo plastic deformation into a cylindrical shape with a predetermined inner diameter. For this reason, if a width of the yoke part 20 is relatively greater than the inner diameter of the yoke part 20 after the lamination, such plastic deformation is not smoothly made.
Besides, another main problem is that cogging torque is generated by interaction between the laminated body 10 and a permanent magnet. “Cogging” refers to an unsmooth movement between a rotor and a stator, and can be referred to as a kind of a torque change. In general, if a protruding portion of the stopping protrusion 35 (formed at an end of the teeth part 30 in a perpendicular direction to the teeth part 30) is formed to be long, an output of the motor can be advantageously increased, and the cogging torque is reduced so that a noise decrease and a constant speed operation can be realized. However, this method has a limit in that, in case of automatically winding a winding coil, the minimum passage of a winding nozzle for automatic winding should be provided. Accordingly, a ripple of an actual output torque should be decreased while the minimum passage for the winding nozzle is provided. Accordingly, a shape of the conventional stopping protrusion 35 is not inappropriate for decreasing the cogging torque.